From U.S. Pat. No. 6,673,033 B1, injector systems for the injection of a fluid in medicinal injection methods and a method for their control are known, wherein the injector system has a drive mechanism with which a fluid to be injected is placed under pressure and a sensor to record a variable that is proportional to the fluid pressure and comprises a pressure monitoring mechanism, which is connected with the sensor and the drive mechanism and interrupts the injection process if the sensor measures a value of the recorded variable that corresponds to a pressure hazard (pressure hazard limit). In order to prevent the fluid pressure from approaching the pressure hazard limit or from exceeding it, provision is also made in the pressure monitoring mechanism so that the drive output of the drive unit is limited to a prespecified limiting value if the variable proportional to the fluid pressure attains a value that corresponds to a prespecified pressure limit (power limiting pressure), wherein this prespecified power limiting pressure is below the pressure hazard limit. The pressure of the fluid to be injected is thereby either indirectly recorded, for example, via the current of an electric motor of the drive mechanism, or directly via a power or pressure transducer, wherein the direct recording of the fluid pressure via a power or pressure transducer is preferred, because this is more accurate and compensates for any tolerances of the injector system. The pressure monitoring mechanism is set up so that it cancels the parameters that are specified by an operator of the injection system and with which the injection system is to be operated and reduces or completely stops the drive power of the drive mechanism, if the recorded fluid pressure is above the prespecified pressure limit for the power reduction (power limiting pressure) or the pressure hazard (pressure hazard limit). By the power reduction of the drive power when the recorded fluid pressure exceeds the prespecified pressure limit of the power reduction (power limiting pressure), it is possible to prevent the pressure hazard limit from being reached at all. If the pressure hazard limit is, nevertheless, reached or even exceeded, the power supply of the drive mechanism is completely shut down, so as to prevent a rise in pressure and thus a hazard threat to the patient or damage to the injection system.
This known injection system and the method for its control prove to be disadvantageous, however, because brief rises of the fluid pressure, which may appear, for example, with the start of the injection system at the beginning of the injection process, can lead to an unnecessary power reduction of the drive power of the drive mechanism, or with very high, brief pressure peaks, can even lead to a complete turning off of the drive mechanism and thus to an interruption of the injection process. This leads to a prolongation of the injection time, in which the patient is to be supplied with a prespecified quantity (dosage) of the fluid to be injected. With an interruption of the injection process, a testing of the system by the operator and a restart of the injection process are necessary, which likewise leads to an undesired prolongation of the time of the injection process and to a reduction of the throughput with a number of injection processes that are to be carried out with the injection system, one after the other.